CHARACTERIZATION OF PT/L-ZEOLITE CATALYSTS BY CHEMISORPTION, EXAFS AND REACTION OF NEOPENTANE WITH H-2

We have prepared four series of Pt/L-zeolite catalysts that were calcined at six different temperatures and subsequently reduced at the same temperature (773K). Two series were prepared by ion exchange and two by impregnation. In all cases the dispersion (H/Pt or CO/Pt) was a maximum after calcination at 543-643 K. The catalysts were further characterized by EXAFS and reaction of neopentane with H-2. There is a good correlation between the particle size determined by chemisorption and the Pt first shell coordination number determined by EXAFS. The neopentane isomerization selectivity ratio was observed to be a linear function of particle size measured by chemisorption or EXAFS coordination number. In addition, enhanced isomerization and hydrogenolysis activities are found to correlate with an increase in the support acidity.